Up Development guide

Query

Last modified on August 15, 2012 17:20

The ability to retrieve persistent data from a database is one of the powerful and useful aspects of DevForce.  At the most basic, such retrieval occurs in one of two ways, either via a query or via a navigation from one entity to another or to a collection of entities. In both of these cases, the underlying mechanism is the same; a query is submitted to and executed by an EntityManager.  

While the most common example of a query is one that operates against a backend relational database, queries may also be constructed so that they operate against a set of data stored in memory on a local machine. One of the most common kinds of query is one that operates against both a backend database as well as a local set of entities with the results combined. This form of query allows a developer to create views of data that represent work in progress.

Queries come in many flavors and may be customized in a variety of ways. The one unifying feature of every DevForce query is that they are all instances of some subclass that implements the IEntityQuery interface.  The EntityManager has a variety of methods that operate on any query type that implements this interface.

The remainder of this chapter will enumerate: 

Created by DevForce on February 08, 2011 12:04

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